Thanks for your question Megan. Unfortunately, we don't have a to-do list feature inside NationBuilder nor do we have any to-do list type third-party app partners.
However, we do have a feature called Paths, Paths in NationBuilder are smaller goals that must be accomplished before moving on to the next. Essentially paths are a series of small steps/tasks that get to an end goal.
You can learn more about NationBuilder paths here: http://nationbuilder.com/create_paths
Complete and current information on how to use NationBuilder is available in the documentation section.